Pipe groove formation

ABSTRACT

Non-metallic, disposable rings are employed in the forming of a groove in the spigot portion of concrete pipe sections. This disposable ring is attached to either the header or the pallet section of a pipe-making form in proper position to form the desired groove in the spigot portion of the concrete pipe section during the making of the concrete pipe section. The ring is made of any rigid, non-metallic disposable material capable of resisting heat, water, alkali and steam. The disposable ring may be left in place when the header and pallet sections of the form are removed from the partially cured pipe. The ring may be removed from the pipe section some time after the pipe section has properly cured, preferably at the time the pipe section is to be used. The possibility of damage to the groove may thus be reduced or eliminated, and the groove may be kept free of dirt and other foreign matter until the pipe section is actually employed during the installation of a line of concrete pipe.

United States Patent Gates 154] PIPE GROOVE FORMATION [72] Inventor:Robert H. Gates, Columbus, Ohio [73] Assignee: Martin MariettaCorporation, New

York, NY.

22 Filed: Oct. 9, 1969 [21] Appl. No.: 865,024

[52] US. Cl. ..264/317, 25/30 C, 25/39, 249/61, 249/100, 264/311,264/318, 264/336 [51] Int. Cl. ..B28b 7/20, B28b 7/34, B28b 21/30 [58]Field of Search ..264/3l3, 317, 318, 333, 334, 264/336, 311; 249/61,100; 25/44, 128 R,

39, 127 R, DIG. 24

[56] References Cited UNITED STATES PATENTS 1,363,912 12/1920 Pauly..264/336 X 2,929,124 3/1960 James ..25/DIG. 24 3,421,551 l/1969 Currier..249/6l X Primary Examiner-Robert F. White Assistant Examiner-J. H.Silbaugh [151 3,683,061 1 Aug. 8, 1972 Attorney-John A. Crowley, Jr. andAlvin l-l. Fritschler ABSTRACT Non-metallic, disposable rings areemployed in the fonning of a groove in the spigot portion of concretepipe sections. This disposable ring is attached to either the header orthe pallet section of a pipe-making form in proper position to form thedesired groove in the spigot portion of the concrete pipe section duringthe making of the concrete pipe section. The ring is made of any rigid,non-metallic disposable material capable of resisting heat, water,alkali and steam. The disposable ring may be left in place when theheader and pallet sections of the form are removed from the partiallycured pipe. The ring may be removed from the pipe section some timeafter the pipe section has properly cured, preferably at the time thepipe section is to be used. The possibility of damage to the groove maythus be reduced or eliminated, and the groove may be kept free of dirtand other foreign matter until the pipe section is actually employedduring the installation of a line of concrete pipe.

17 Claims, 1 Drawing Figure PIPE GROOVE FORMATION BACKGROUND OF THE.INVENTION 1 Field of the Invention This invention relates to concretepipe sections. More particularly, it relates to an improved process forthe manufacture of such pipe sections and means for preserving suchsections prior to use.

2. Description of the Prior Art Large quantities of concrete pipesections are produced every year by various techniques such as the wetcast, dricast and machine processes. In such processes, concrete mixesare placed in a pipe-making form to produce pipe sections from which theforms are stripped either immediately or at some later time. Newlyformed concrete pipe sections are generally passed through a kiln withthe header and pallet sections of the pipe-making form in place. Afterpassing through the kiln, the pipe section is generally transferred to acuring yard where the header and pallet are removed from the partiallycured pipe. The concrete pipe section at this point is in a relativelygreen state with curing being fully completed within a period of 3 to 28days.

Concrete pipe sections produced by the various known methods havegrooves formed in the spigot portion thereof by the use of reusable snaprings. These rings, typically made of cold rolled steel, are attached toeither the header or the pallet section of the pipemaking form and arepositioned so as to form the desired groove in the spigot portion of theconcrete pipe section. The size and shape of the steel snap ring isdetermined by the desired size and shape of the spigot groove. When thepipe section is formed with its bell portion down, the steel snap ringis attached to the upper or header section of the pipe-making form. Whenthe concrete pipe section is made with its bell portion up, on the otherhand, the steel snap ring is attached to the lower or pallet section ofthe pipe-making form, so that the groove may be formed in the spigotportion of the concrete pipe section.

In actual concrete pipe production, it is necessary that each steel snapring he used continually with a particular header or pallet section ofthe pipe-making form. As a result, it is conventional practice to removethe steel snap ring at the same general time that the pallet or headerare removed from the partially cured pipe section in the curing yard.The steel snap ring is thereafter thoroughly cleaned and transportedback from the curing yard to the pipe manufacturing location to bematched up with its associated pallet or header sections for re-use inthe manufacture of additional concrete pipe sections. While such steelsnap rings are suitable for forming the desired groove in the spigotportion of each concrete pipe sections, the cost of each snap ring andthe necessity for cleaning it and for assuring its return for furtheruse with a particular pallet or header constitute objectionable featuresof present pipe-making practice.

The steel snap rings are recovered in the curing yard by prying therings apart to free them from newly formed concrete pipe sections. Theparticular force thus required to pry apart the ring sometimes causesthe snap ring to become distorted out of its required shape. This isparticularly true with respect to the snap rings employed for small pipesizes, such as those on the order of from about 6 inches to about 24inches in diameter. Even in larger pipe sizes, however, steel snap ringsrequire considerable effort for their removal, and the possibility ofdistortion exists. The reconditioning or replacement of such steel snaprings constitutes an additional item of expense for the producers ofconcrete pipe sections.

Because of the difficulty in removing such steel snap rings from thepipe and the relatively green state of the concrete pipe sections at thetime the rings are removed, an undesirably high incidence of spigotgroove damage is normally encountered. Up to about 10 percent of thepipe sections produced by conventional techniques, for example,generally have some form of groove damage occasioned by steel snap ringremoval. In some instances, this groove damage may be repaired byspecial patching methods. An estimated percent to percent of the damagedpipe may thus be repaired and ultimately shipped to its destination. Theremaining 20 percent to 30 percent of the damaged pipe, however, aresubjected to rejection and, as such, are unusable except as second-gradepipe at a greatly reduced selling price.

To avoid this problem, the groove-forming reusable ring is sometimesmade in two semicircular sections for ease of removal. For maintenanceof a proper joint configuration, however, this technique requires theuse of matched ring section sets. This, again, is difficult to control,and requires further provisions for setting and maintaining alignmentwhere the semicircular sections oin.

The economic and technical necessity for removing the steel snap ringfrom a partially cured concrete pipe section not only subjects thespigot groove to potential damage during ring removal, but subjects thegroove to the risk of further damage in yarding, handling, loading andunloading and shipping to its point of use.

After the spigot groove has thus been exposed by the removal of thesteel snap ring, the groove is susceptible to the collection of grit,dirt, grease and other foreign matter that would be damaging to theround rubber gasket subsequently placed in the spigot groove when thepipe sections are joined, spigot to bell, to form a line of pipe.Specifications generally require that the spigot groove shall be cleanand free from all grit, dirt, grease and other foreign matter at thetime pipe sections are installed. Concrete pipe sections are generallydelivered and strung out along the job sometime prior to laying. Insewer jobs and similar applications, all types of dirt and foreignmatter can collect in an exposed groove between the time of delivery andinstallation. The necessity for taking additional preventive action orof efiecting a thorough cleaning of the spigot groove on site representsa further disadvantageous feature of conventional concrete pipeapplications.

It is an object of the present invention, therefore, to provide animproved process for the production of concrete pipe sections.

It is another object of the invention to provide an improved process forthe forming of the groove in the spigot portion of said concrete pipesections.

It is another object of the present invention to provide a method forreducing damage to the spigot grooves of concrete pipe sections.

It is a further object of the invention to provide a method formaintaining the spigot grooves of concrete pipe sections clean and freefrom dirt and other foreign matter prior to use in pipe-layingapplications.

With these and other objects in mind, the present invention ishereinafter described in detail, and the novel features thereof areparticularly pointed out in the appended claims.

SUMMARY OF THE INVENTION The groove in the spigot portion of a concretepipe section is formed by the use of a non-metallic disposable ring inconjunction with the conventional header and pallet sections of apipe-making form. The disposable ring is attached to either the headeror the pallet in proper position to form the desired spigot groove.After the heat treatment of the newly formed pipe in a kiln, the headerand pallet are removed from the pipe. The disposable ring, however, maybe left in place on the pipe until after the pipe has fully cured.Preferably, the pipe may be shipped to its point of use with thedisposable ring still in place, so as to protect the groove frompossible damage and the accumulation of dirt and other foreign matter.

The disposable ring may be made from any suitable non-metallic materialthat is rigid and resistent to heat, water, alkali and steam. Because ofthy very low cost of such a disposable ring, it may simply be discardedwhen it is removed from the pipe.

BRIEF DESCRIPTION OF THE DRAWING The invention is hereunder describedwith reference to the accompanying drawing in which the single FIGURE isa partial sectional view of a concrete pipe section showing the relativepositioning of the header and pallet sections of a pipe-making form andthe position of the disposable ring in one particular embodimentthereof.

DETAILED DESCRIPTION OF THE INVENTION The disposable groove-forming ringof the present invention may be made of any convenient non-metallicmaterial that is of a rigid nature and is resistant to the types ofenvironment encountered in the production of concrete pipe sections.Thus, the material should be resistant to heat, water, alkali and steam.While the particular material from which the disposable ring is made isnot a critical feature of the present invention, the ring canconveniently be made from such materials as paper or cardboard, leather,leather substitutes, hemp, fabric, fiberglass, wood, plastics andrubber. Disposable paper rings made from either reconstituted paperwaste or chip board, such as the rings made from either of thesematerials by the George 0. Jenkins Company, have been found particularlysuitable and economical for the purposes of the present invention.

It is also within the scope of the present invention to employ treatedmaterials, such as a resin-impregnated paper or an oil-treated paper inthe formation of the disposable rings herein contemplated. Likewise, itis within the scope of the present invention to treat a preformed ringprior to its use in order to enhance its resistance to theabove-indicated environments.

As used herein, the term non-metallic disposable ring is meant toinclude groove-forming rings made of any suitable non-metallic materialthat permits the economical use of the ring on a single, or one-shot,basis in accordance with the teachings of the present invention. Whilean economic determination concerning the use of disposable, throw-awayrings may conveniently be expressed in terms of the cost of thedisposable ring vis-a-vis steel snap rings with relation to the cost ofthe particular concrete pipe section being produced, it will beappreciated that this determination is made not only on the basis of thecost per se, but also in light of the practical production and operatingadvantages obtainable in the practice of the present invention. Thesignificance of these advantages tends to greatly enhance the commercialfeasibility of employing non-metallic disposable rings in place ofconventional steel snap rings.

For purposes of this invention, the cost of such nonmetallic disposablerings will generally range from about 4-5 percent, up to about 25-30percent, of the product price per foot of the length of the pipe sectionproduced. The cost preferably will be from about 4-5 percent to about8-10 percent. It is economically feasible to leave each ring in theformed pipe groove in accordance with the present invention to protectthe groove from damage and dirt accumulation. The cost of conventionalsteel snap rings, by contrast, generally ranges from about percent forlarger diameters of produced pipe to about 400 percent for the smallerdiameter sizes. For the practical technical and economic reasons setforth above, such steel rings cannot be used in the manner disclosed andclaimed herein.

The size and shape of the non-metallic, disposable ring will be the sameas that of the steel snap rings used in conventional practice. Suchrings are usually of circular configuration, with a rectangular ortrapezoidal cross-section equal in size to the size of the desiredgroove in the spigot portion of the concrete pipe. Steel snap rings arecommonly provided with a radial split therein for ease of application,and the non-metallic, disposable rings of the present invention maylikewise contain a radial split, if desired, although such a split isnot necessary to the proper use of the disposable rings. As withconventional steel snap rings, the disposable rings may be attached toeither the header or the pallet section of the pipe-making form,depending upon the manner in which the pipe is to be formed. Concretepipe sections are conventionally formed with the pallet portion of theform on the bottom and the header portion on the top. If the pipesection is formed with its bell portion down, the ring is attached tothe inner surface of the header portion of the form in order to form thedesired groove in the spigot portion of the pipe. If, on the other hand,the pipe section is formed with its bell portion up, the disposable ringis attached to the pallet portion of the form so as to likewise form thedesired groove in the spigot portion of the concrete pipe section.

The disposable ring may be secured to either the header or the palletsection of the pipe-making form by any convenient means. When thematerial from which the ring is made is of a liquid absorbent nature andtends to swell when wet, the disposable ring may be convenientlyattached by soaking the ring in the liquid and thereafter positioning itin its proper location of either the header or the pallet portions ofthe form. As the wet ring tends to expand, a tight fit between the ringand the pipe-making form is obtained, so as to hold the ring in itsproper position during the formation of the pipe. A paper ring may, forexample, be soaked in water for this purpose. If the ring has beenoil-treated or otherwise made non-water or other liquid absorbent,however, this technique cannot be employed.

In other embodiments of the invention, the disposable ring may beretained in its proper groove-forming position by mechanical means. Forexample, a mechanical catch, such as a pin or a capscrew, may be passedthrough either the header or pallet portions of the form so as toprotrude very slightly under the disposable ring, so as to catch or holdthe disposable ring in its desired position and to prevent its fallingtherefrom. For this purpose, the mechanical catch need only extend veryslightly past the inner surface of either the header or the pallet, forexample, on the order of about three thirty-seconds inch.

In conventional pipe section production, the newly formed pipe is passedinto a kiln with its pallet and header portions in place on the pipe.After a period of about 12 to 24 hours, the pipe is transferred to acuring yard where the pallet and header are removed from the pipe. Thesteel snap ring employed in conventional practice is removed at the sametime as the pallet and header sections. As discussed above, the risk ofdamage to the green concrete during the removal of the snap ring isconsiderable. In addition, the groove in the partially cured pipe isthereafter susceptible to damage, unless other means are taken toprotect it from damage while it is in storage in the curing yard andthereafter in the subsequent handling, loading, unloading and transportof the pipe. Since the disposable, non-metallic ring of the presentinvention need not be returned to the pipe-making location for re-use,there is no necessity, in the practice of the present invention, forremoving the ring from the pipe until the concrete in the pipe has fullycured. Advantageously, the disposable ring may be retained in the spigotgroove during the entire time the pipe section is in the curing yard andthereafter until it is ready for use in the installation of a line ofpipe. As a result, the ring is in effect embedded in the spigot groove,the cross sectional size of the groove being equal, of course, to thatof the ring around which the concrete is placed. The small amount ofadhesion that will exist between the ring and the concrete in which itis thus embedded provides an inherently tight seal that prevents dirtand other foreign matter from accumulating in the groove, while alsopreventing inadvertent damage to the groove as a result of chipping andthe like.

Referring now to the drawing, the concrete pipe section illustratedtherein has a bell portion 1 and a spigot portion 2. In the formation ofthe pipe with its bell portion down, header section 3 of the pipe-makingform is positioned at the spigot end of the pipe section and palletsection 4 is positioned at the bell portion of the pipe section. Theinner section of the pipe-making form is not shown in the drawing. Thedesired groove in spigot portion 2 is formed by means of disposable ring5 attached to the inner pipe-contacting surface of header section 3. Asin conventional practice, the concrete pipe section is fonned withlongitudinal steel rods 6 and circumferential steel rods 7 forreinforcement.

In the illustrated embodiment, mechanical means are employed forretaining disposable ring 5 in its proper groove-forming position. Thus,capscrew 8 passes through header 3 and projects slightly into the spigotarea so as to prevent disposable ring from dropping out of itspre-determined position. Slight indentations in the concrete in theouter surface of the spigot portion beneath the groove therein willnaturally result at the points at which such cap screws are employed.

In the field, a line of pipe is installed by inserting the spigotportion of one pipe section in the bell portion of the adjoiningsections. A rubber gasket is set in each spigot groove so as to sealeach assembled bell and spigot joint. The disposable ring in the presentinvention not only is used to form the spigot groove, but also to act asa groove-protecting packing because of its inherently tight fit in thegroove portion of the concrete pipe secton.

Highly significant advantages effecting both the production and use ofconcrete pipe are obtainable by means of the present invention.Elimination of the need for conventional steel snap rings that must bereused for reasons of economy serves to avoid the necessity for cleaningsuch rings after removal from the pipe and the time and expense involvedin transporting the rings back from the curling yard to the productionarea. The practical necessity for matching a particular steel snap ringwith a particular header or pallet throughout the production cycle isavoided. The additional inconvenience and cost of occasional repair ofdamaged rings is also eliminated. The necessity for replacement of therelatively expensive steel snap rings, due to damage or misplacement, islikewise overcome by the use of very inexpensive, disposable rings thatare not intended for reuse.

In addition to such production advantages, the present invention greatlyreduces or eliminates the damage to the spigot groove that frequentlyoccurs in conventional operations. A major cause of groove damage is thepractical necessity for removing the metallic snap ring while theconcrete in the pipe is still in a green state. Since the disposablerings employed in the present invention are to be thrown away after oneuse, there is no necessity for removing the rings from green concrete.The disposable rings may readily be left in place on the pipe until theconcrete has completely cured. This normally requires a period of atleast three days.

Leaving a disposable groove-forming ring in place on the concrete pipealso serves to greatly reduce the likelihood of groove damage duringsubsequent handling, loading, unloading, storage and transporting of theconcrete pipe section. The tightly fitting disposable ring tends toassist the concrete in absorbing bumps or blows that might otherwisetend to break off the edge of the groove or otherwise damage it, so thatthe pipe no longer meets specifications. As much as percent or more ofthe groove damage of this type can be avoided by retaining thedisposable ring in the spigot groove as provided in this application.This represents a major cost saving for pipe producers who wouldotherwise be required to undertake costly patching operations or to sellrejected pipe as second grade pipe at a greatly reduced price.

The additional major advantage of the present invention is of particularbenefit to contractors or pipe installers. Contract specificationsgenerally require that the gasket recess, i.e., the spigot groove, shallbe clean and free from dirt, grit, oils and/or other foreign matter atthe time the pipe is installed. Concrete pipe sections are ordinarilydelivered to a job site and strung out in line sometimes prior to theactual laying of the pipe. Sewer construction and various otherapplications for concrete pipe are essentially dirty operations, and aconsiderable amount of dirt and foreign matter tends to collect in thespigot groove between the time of delivery of the pipe to the job siteand the time of installation. This generally requires that the groove bethoroughly cleaned prior to installation. With the disposable ringstightly fitting in the spigot grooves, however, the pipe sections may bekept entirely free from the accumulation of dirt and other foreignmatter in their spigot grooves until the pipe section is actuallyinstalled. This saving of labor and expense in the field furtherenhances the revolutionary improvement in the concrete pipe art that isachieved by means of this invention.

While the invention has been described herein with respect to particularembodiments thereof, it will be appreciated that various changes andmodifications can be made therein without departing from the scope ofthe invention as set forth in the appended claims.

Therefore, I claim:

1. A process for forming a groove in the spigot portion of a concretepipe section comprising:

a. attaching a non-metallic disposable ring to the inner,pipe-contacting surface of the header section of a pipe-making form,said ring having a rigid nature and comprising a heat, water, alkali andsteam resistant material conforming in size and position on said headerto the desired size and position of the groove in the spigot portion ofsaid pipe section;

. forming said concrete pipe section with its spigot end up and incontact with the inner surface of said header section;

c. subjecting said concrete pipe section to heat treatment while in itspipe-making form with the disposable ring in its predetermined positionon the inner surface of said header; removing said header and the palletsection of the pipe-making form from said heat-treated concrete pipesection prior to the curing of said pipe section beyond the green statewhile retaining said disposable ring in groove-defining position on thesurface of said pipe section;

e. curing said pipe section beyond the green state and thereafterremoving said disposable ring from the spigot portion of said concretepipe section so as to uncover the desired groove in said pipe section;and

f. discarding said disposable ring thus removed from the cured pipesection, said ring not being employed in the formation of spigot groovesin subsequently produced concrete pipe sections,

whereby the likelihood of groove damage caused by the removal of ametallic snap ring from the pipe section in its relatively green stateprior to complete curing is avoided, the necessity for cleaning andtransporting such a metallic or other reusable snap ring back from thecuring yard to the pipe manufacturing location for reuse with aparticular pallet-header combination is entirely obviated, and thegroove in the spigot portion of the pipe section may be kept free ofgrit, dirt, grease and other foreign matter by said disposable ring uptothe time said section is used in the installation of a line of concretepipe.

2. The process of claim 1 in which said pipe section has an internaldiameter of from about 6 inches to about 24 inches, said concrete pipesection being completely cured before said disposable ring is removedfrom the spigot portion thereof.

3. The process of claim 1 in which said non-metallic disposable ringcomprises a paper ring.

4. The process of claim 3 in which said paper ring is oil-treated toimprove its moisture resistance.

5. The process of claim 1 in which said non-metallic disposable ringcomprises a plastic ring.

6. The process of claim 1 in which said non-metallic disposable ringcomprises a rubber ring.

7. The process of claim 1 in which said disposable ring is attached tothe inner surface of said header section by positioning a mechanicalcatch on said surface on the underside of said disposable ring toprevent said ring from falling from its pre-determined position on theinner surface of said header.

8. The process of claim 1 in which said disposable ring comprisesaliquid absorbent material and including soaking the ring in said liquidprior to placing the ring in its desired position on the header, the wetring tending to swell in position so as to provide a tight fit on theinner surface of the header.

9. The process of claim 8 in which said liquid is water.

10. The process of claim 1 in which said disposable ring has arectangular cross-sectional area.

11. The process of claim 1 in which said disposable ring has atrapezoidal cross-sectional area.

12. A process for forming a groove in the spigot portion of a concretepipe section comprising:

a. attaching a non-metallic disposable ring to the inner,pipe-contacting surface of the pallet section of a pipe-making form,said ring having a rigid nature and comprising a heat, water, alkali andsteam resistant material conforming in size and position on said palletsection to the desired size and portion of the groove in the spigotportion of said concrete pipe section;

b. forming said concrete pipe section with its bell end up, with itsspigot end down and in contact with the inner surface of said palletsection;

0. subjecting said concrete pipe section to heat treatment while in itspipe-making form with the disposable ring in its predetermined positionon the inner surface of said pallet section;

d. removing the header section and the pallet section of the pipe-makingform from said heat-treated concrete pipe section prior to the curing ofsaid pipe section beyond the green state while retaining said disposablering in groove-defining position on the surface of said pipe section;

e. curing said pipe section beyond the green state and thereafterremoving said disposable ring from the spigot portion of said concretepipe section so as to uncover the desired groove in said pipe section;and

f. discarding said disposable ring thus removed from 1 the cured pipesection, said ring not being employed in the formation of spigot groovesin subsequently produced concrete pipe sections,

whereby the likelihood of groove damage caused by the removal of ametallic snap ring from the pipe section while said section is in itsrelatively green state prior to complete curing is avoided, thenecessity for cleaning and transporting such a metallic or otherreusable snap ring back from the curing yard to the pipe manufacturinglocation for reuse with a particular pallet-header combination isentirely obviated, and the groove in the spigot portion of the pipesection may be kept free of grit, dirt, grease and other foreign matterby said disposable ring up to the time said section is used in theinstallation of a line of concrete pipe.

13. The process of claim 12 in which said ring comprises a paper ring,said concrete pipe section being completely cured before said disposablering is removed from the spigot portion thereof.

14. The process of claim 12 in which said ring comprises a plastic ring.

15. The process of claim 12 in which said ring comprises a rubber ring.

16. The process of claim 12 in which said disposable ring has arectangular cross-sectional area.

17. The process of claim 12 in which said ring has a trapezoidalcross-sectional area.

1. A process for forming a groove in the spigot portion of a concretepipe section comprising: a. attaching a non-metallic disposable ring tothe inner, pipecontacting surface of the header section of a pipe-makingform, said ring having a rigid nature and comprising a heat, water,alkali and steam resistant material conforming in size and position onsaid header to the desired size and position of the groove in the spigotportion of said pipe section; b. forming said concrete pipe section withits spigot end up and in contact with the inner surface of said headersection; c. subjecting said concrete pipe section to heat treatmentwHile in its pipe-making form with the disposable ring in itspredetermined position on the inner surface of said header; d. removingsaid header and the pallet section of the pipemaking form from saidheat-treated concrete pipe section prior to the curing of said pipesection beyond the green state while retaining said disposable ring ingroove-defining position on the surface of said pipe section; e. curingsaid pipe section beyond the green state and thereafter removing saiddisposable ring from the spigot portion of said concrete pipe section soas to uncover the desired groove in said pipe section; and f. discardingsaid disposable ring thus removed from the cured pipe section, said ringnot being employed in the formation of spigot grooves in subsequentlyproduced concrete pipe sections, whereby the likelihood of groove damagecaused by the removal of a metallic snap ring from the pipe section inits relatively green state prior to complete curing is avoided, thenecessity for cleaning and transporting such a metallic or otherreusable snap ring back from the curing yard to the pipe manufacturinglocation for reuse with a particular pallet-header combination isentirely obviated, and the groove in the spigot portion of the pipesection may be kept free of grit, dirt, grease and other foreign matterby said disposable ring up to the time said section is used in theinstallation of a line of concrete pipe.
 2. The process of claim 1 inwhich said pipe section has an internal diameter of from about 6 inchesto about 24 inches, said concrete pipe section being completely curedbefore said disposable ring is removed from the spigot portion thereof.3. The process of claim 1 in which said non-metallic disposable ringcomprises a paper ring.
 4. The process of claim 3 in which said paperring is oil-treated to improve its moisture resistance.
 5. The processof claim 1 in which said non-metallic disposable ring comprises aplastic ring.
 6. The process of claim 1 in which said non-metallicdisposable ring comprises a rubber ring.
 7. The process of claim 1 inwhich said disposable ring is attached to the inner surface of saidheader section by positioning a mechanical catch on said surface on theunderside of said disposable ring to prevent said ring from falling fromits pre-determined position on the inner surface of said header.
 8. Theprocess of claim 1 in which said disposable ring comprises a liquidabsorbent material and including soaking the ring in said liquid priorto placing the ring in its desired position on the header, the wet ringtending to swell in position so as to provide a tight fit on the innersurface of the header.
 9. The process of claim 8 in which said liquid iswater.
 10. The process of claim 1 in which said disposable ring has arectangular cross-sectional area.
 11. The process of claim 1 in whichsaid disposable ring has a trapezoidal cross-sectional area.
 12. Aprocess for forming a groove in the spigot portion of a concrete pipesection comprising: a. attaching a non-metallic disposable ring to theinner, pipe-contacting surface of the pallet section of a pipe-makingform, said ring having a rigid nature and comprising a heat, water,alkali and steam resistant material conforming in size and position onsaid pallet section to the desired size and portion of the groove in thespigot portion of said concrete pipe section; b. forming said concretepipe section with its bell end up, with its spigot end down and incontact with the inner surface of said pallet section; c. subjectingsaid concrete pipe section to heat treatment while in its pipe-makingform with the disposable ring in its predetermined position on the innersurface of said pallet section; d. removing the header section and thepallet section of the pipe-making form from said heat-treated concretepipe section prior to the curing of said pipe section beyond the greenstate while retaining said disposable ring in groove-defininG positionon the surface of said pipe section; e. curing said pipe section beyondthe green state and thereafter removing said disposable ring from thespigot portion of said concrete pipe section so as to uncover thedesired groove in said pipe section; and f. discarding said disposablering thus removed from the cured pipe section, said ring not beingemployed in the formation of spigot grooves in subsequently producedconcrete pipe sections, whereby the likelihood of groove damage causedby the removal of a metallic snap ring from the pipe section while saidsection is in its relatively green state prior to complete curing isavoided, the necessity for cleaning and transporting such a metallic orother reusable snap ring back from the curing yard to the pipemanufacturing location for reuse with a particular pallet-headercombination is entirely obviated, and the groove in the spigot portionof the pipe section may be kept free of grit, dirt, grease and otherforeign matter by said disposable ring up to the time said section isused in the installation of a line of concrete pipe.
 13. The process ofclaim 12 in which said ring comprises a paper ring, said concrete pipesection being completely cured before said disposable ring is removedfrom the spigot portion thereof.
 14. The process of claim 12 in whichsaid ring comprises a plastic ring.
 15. The process of claim 12 in whichsaid ring comprises a rubber ring.
 16. The process of claim 12 in whichsaid disposable ring has a rectangular cross-sectional area.
 17. Theprocess of claim 12 in which said ring has a trapezoidal cross-sectionalarea.